1. Field of the Invention
The present invention relates generally to an apparatus and method for controlling a camera function in a device with a digital camera function, and more particularly, to an apparatus and method for reducing a shutter lag of a digital camera.
2. Description of the Related Art
A device with a digital camera function, like a mobile wireless terminal equipped with a camera module, starts a preview mode in which a user can view preview images in real time, when the user chooses the camera function. If the user decides on a photographing target while viewing preview images in the preview mode, the user first presses a half shutter to perform Auto Focus (AF), and then presses a full shutter at a desired time to take a picture. At this moment, mode switching (or mode transition) takes place from the preview mode to a capture mode, in which the picture is stored.
A series of operations, including the mode switching, requires time. So, actually, the user gets a picture taken at a time delayed by some extent from the time the shutter is pressed, rather than obtaining a picture taken at the exact moment the shutter is pressed. Such delay is referred to as a ‘shutter lag’. In other words, the shutter lag refers to a time from the moment the user pressed the shutter until the time a picture capture function starts. Because of the shutter lag, the user cannot get the picture taken at the exact time he actually desired.
Generally, in a cell phone's camera, an AF time of about 0.5 to 1 second is required and a shutter lag of 0.1 to 0.3 seconds occurs. Since the user knows the fact that though the shutter lag is shorter than an AF lag, which is the time required for focusing, the picture is taken after a delay rather than being taken at the moment the shutter is pressed, user satisfaction with the captured image may fall.
Many attempts to exclude the switching process from the preview mode to the capture mode using full-pixel preview have been made to reduce the shutter lag.
For example, to accomplish a zero shutter lag, Scalado AB has introduced a technology for burying a hardware Joint Photographic Coding Experts Group (JPEG) compression function and a large-capacity buffer memory in a device with a camera module, compressing multiple full-pixel frames, and storing the frame captured at the time closest to the moment the shutter was pressed by a user. However, use of this technology additionally increases the cost and causes power consumption due to encoding and decoding for the compression.